This explanation for the concentration of copper and reducing it by cooling and skinning is effective but could also explain why the analysis is so high. Taking the sample from this region would give a high number. If you are not already doing so try taking your sample by collecting material in your ladle from the wave itself after pot has been on and up to temperature for a few hours. This will ensure the pot is evenly mixed and sample is representative of what is going onto boards. Also best practise dictates that the sample is then chill cast for all the same reasons. Mike Fenner Indium Corporation of Europe T: + 44 1908 580 400 F: + 44 1908 580 411 M: + 44 7810 526 317 W: www.indium.com -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Furrow, Robert Gordon (Bob) Sent: Wednesday, August 15, 2001 3:08 PM To: [log in to unmask] Subject: Re: [TN] Solder analysis results I am not sure that it is stratification so much as different solubility levels at different temperatures. The copper in a solder bath does not stay as elemental copper, but rather forms a tin/copper compound. The solubility of the tin/copper compound in tin/lead decreases with temperature. As you lower the pot temperature the tin/copper will come out of solution and since it less dense than the bulk tin/lead will accumulate on the top of the pot along with dross. The tin/copper rich compound looks like tiny needles/slivers in the dross. By skimming this out of the pot you remove much more copper (and also tin) than you do lead and thereby drop the copper concentration. To get the copper to stay in solution up to a concentration of 1.7%, it seems to me the solder pot temperature must have been elevated, because in my experience, even at normal operating temperatures and daily dross skimming, the copper level is hard to get above 0.5%. Thanks, Robert Furrow Printed Wiring Board Engineer Strategic Supply Global Account Manager Supply Chain Networks Lucent Technologies 978-960-3224 [log in to unmask] -----Original Message----- From: Lou Hart [mailto:[log in to unmask]] Sent: Wednesday, August 15, 2001 9:21 AM To: [log in to unmask] Subject: Re: [TN] Solder analysis results Any comment on Steve's stratification theory? A few years back I had SPC charts at a HASL pot at a PC fab, with analysis every two weeks. Cu content stayed 0.21% to 0.24% over a period of 1+ years, even though all we were doing was skimming stuff off the top. Lou Hart -----Original Message----- From: Stephen R. Gregory [SMTP:[log in to unmask]] Sent: Tuesday, August 14, 2001 10:04 PM To: [log in to unmask] Subject: Re: [TN] Solder analysis results Dave, Surely, not ALL 1700-lbs.? Wooo-doggies! I can only imagine what a task that would be!!! I've read some stuff that if you keep the pot static, and keep it at a stable temperature for a period (what this really is, I don't know...there's varying opinions), the metals will seek their own level (according to the different opinions, the copper will be towards the top), then you scoop out out the top layer, and replenish what you've removed with fresh bars. The question that I have though, how did the pot get so out of balance with copper? I've never had a problem with copper content, even when waving OSP boards...tin levels dropping, yes. But not excessive copper...somebody throw some pennies in the pot? -Steve Gregory- > RJ Klien Wassink suggests [bible p 169] pouring contaminated solder at about > 190?C through a 20 mesh stainless steel stariner to reduce copper content to > 0.25%. > > Dave Fish > << File: ATT00002.htm >> ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------